In a typical wheel end assembly, a brake rotor may be fitted to the mounting flange of the rotating bearing ring of the hub unit. The wheel rim is then mounted against the brake rotor and both are bolted to the wheel mounting flange. The hub-rotor interface is exposed to atmospheric corrosion from humid air and from salt water. The corrosion leads to the formation of rust on and between the contacting surfaces of the wheel mounting flange, brake rotor and wheel rim. The layer of corrosion that forms on the wheel mounting flange surface results in increased runout, which may exceed that specified for finished and assembled hub units of e.g. 10 to 15 micro meters. When vehicles are serviced and undergo replacement of a brake rotor, the fixation of a (new) brake rotor on a wheel mounting flange having corrosion on the contact surface for the brake rotor would lead to axial runout and brake shudder.
US 2006/0177169 A1 discloses a hub unit with a wheel mounting flange for mounting a wheel on the hub. The flange is provided with a rust-preventive layer on the surface receiving the wheel. This rust-preventive layer may be a fused ceramics material or a plastic material either moulded onto the surface by insert moulding or a separate part fixed to the surface by an adhesive.
EP 0 800 011 A2 discloses a corrosion-protective element for protecting junctions between metal components made of different metals against electrolytic corrosion when exposed to moisture by providing a shield of sheet metal which is electrically passivated or has an anti-corrosion coating on its opposite surfaces.
It is further known to provide electrolytic zinc plating on the hub flange surface to prevent corrosion. The electrolytic plating is usually a bath process where at least the component in which the flange is formed is submerged in molten zinc and subjected to high temperature (over 150° C.) baking to eliminate hydrogen embrittlement.